Burning mouth usually occurs in individuals over 50, but can affect others as well. There are several reasons why it occurs.
Denture problems: a new denture, or one that doesn't fit well, can irritate your entire mouth.
Reduced salivary gland function: this will cause the mouth to become dry, inviting oral discomfort, difficulty eating or swallowing, loss of taste, and a burning mouth. Salivary gland dysfunction sometimes comes with age. But there are saliva substitutes and rinses to protect your oral tissues, and soothe burning sensations.
Medications: these often dry the mouth (side effects)
Vitamin deficiency: there is some evidence linking burning mouth syndrome to Vitamin B deficiency.
Candida infections: this is a common oral fungus, usually apparent to the eye but sometimes undetectable. A topical anti-fungal agent can be prescribed.